1. Field of the Invention
This invention relates to an electro-luminescence display (ELD), and more particularly to an organic electro-luminescence device and a fabricating method thereof wherein an organic light-emitting layer can be provided at an accurate location to prevent a deterioration of picture quality.
2. Description of the Related Art
Recently, there have been developed various flat panel display devices reduced in weight and bulk that is capable of eliminating disadvantages of a cathode ray tube (CRT). Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP) and an electro-luminescence display device (ELD), etc. Particularly, the ELD has a structure in which electrodes are attached onto each side of an organic light-emitting layer basically consisting of a hole carrier layer, a light-emitting layer and an electron carrier layer. The ELD has been highlighted to be a post-generation flat panel display device owing to characteristics of a wide viewing angle, a high aperture ration and a high chromaticity, etc.
Such an ELD is largely classified into an inorganic ELD and an organic ELD depending upon its used material. The organic ELD has an advantage in that it can be driven with a lower voltage than the inorganic ELD because electrons and holes emit a light while being extinguished after making a pair when electric charges are injected into an organic EL layer provided between a hole injection electrode and an electron injection electrode. Further, the organic ELD has advantages in that it can be formed on a flexible transparent substrate such as plastic and can be driven with a lower voltage (i.e., less than 10V) than the PDP or the inorganic ELD; and it has a relatively small power consumption and an excellent color sense.
FIG. 1 is a perspective view showing a structure of a conventional organic ELD.
Referring to FIG. 1, the organic ELD has an anode electrode 4 and a cathode electrode 12 provided on a substrate 2 in a direction crossing each other.
A plurality of anode electrodes 4 are provided on the substrate 2 in such a manner to be spaced at a desired distance. An insulating film (not shown) having an aperture for each EL cell area is formed on the substrate 2 provided with the anode electrodes 4. On the insulating film, barrier ribs 8 for separating an organic light-emitting layer 10 and the cathode electrode 12 to be provided thereon are positioned. The barrier rib 8 is provided in a direction crossing the anode electrode 4, and has a backward taper structure in which its upper portion has a larger width than its lower portion. The organic light-emitting layer 10 made from an organic compound and the cathode electrode 12 are entirely deposited onto the insulating film provided with the barrier rib 8. The organic light-emitting layer 10 has a hole carrier layer, a light-emitting layer and an electron carrier layer deposited onto the insulating film. Such a passive ELD emits electrons and holes when a driving signal is applied to the anode electrode 4 and the cathode electrode 12. The electrons and holes emitted from the anode electrode 4 and the cathode electrode 12 are re-combined within the organic light-emitting layer 10 to generate a visible light. The generated visible light outputs to the exterior via the anode electrode 4 to thereby display a desired picture or image.
Hereinafter, a method of fabricating the conventional organic ELD will be described with reference to FIG. 2A to FIG. 2D.
Firstly, as shown in FIG. 2A, the anode electrode 4 is provided by depositing a metal transparent conductive material onto the substrate 2 made from a soda lime or a vulcanized glass and then patterning it by the photolithography and the etching process. Herein, indium-tin-oxide (ITO) or SnO2 is used as the metal material.
The insulating film (not shown) is formed in such a manner to expose a light-emitting area by coating a photosensitive insulating material onto the substrate 2 provided with the anode electrode 4 by the spin coating technique and then patterning it by the photolithography and the etching process.
As shown in FIG. 2B, the barrier rib 8 is formed by depositing a photosensitive organic material onto the insulating film and then patterning it by the photolithography and the etching process. The barrier rib 8 is provided to divide the pixels in such a manner to cross the plurality of anode electrodes 4.
As shown in FIG. 2C, the organic light-emitting layer 10 is formed on the substrate 2 provided with the barrier rib 8 by utilizing a shadow mask (not shown).
As shown in FIG. 2D, the cathode electrode 12 is formed by depositing a metal material onto the substrate 2 provided with the organic light-emitting layer 10.
Meanwhile, the formation of the organic light-emitting layer 10 by utilizing the conventional shadow mask raises a problem in that an organic light-emitting material passing through a slit of the shadow mask is not secured at an accurate location to generate a formation badness of the organic light-emitting layer 10, thereby causing a deterioration of picture quality.
This will be described in detail with reference to FIG. 3 below.
When a heating vessel 20 contained with a specific organic material (e.g., a light-emitting material 21 for implementing a red (R) color) is heated, the specific organic material 21 (e.g., a light-emitting material 21 for implementing a red (R) color) within the heating vessel 20 is sublimed to be deposited onto the anode electrode 4. Herein, a shadow mask 22 is provided in such a manner to be spaced at a desired distance from the anode electrode 4 as the barrier rib 8 is formed on the barrier rib. Further, as a process tolerance is generated upon fabricating the shadow mask 22, the specific organic material 21 having passed through a slot 24 of the shadow mask 22 is widely spread. Thus, there is raised a problem in that a deposition of it onto the adjacent sub-pixel for implementing a different color (i.e., the sub-pixel for implementing a green (G) color or a blue (B) color) occurs frequently.
Therefore, the formation badness of the organic light-emitting layer 10, such as a mixing of different color organic light-emitting material at each sub-pixel (i.e., R, G or B sub-pixel), or a formation of improper amount of organic light-emitting material, is generated to cause a deterioration of picture quality such as a non-uniformity of picture quality upon a light-emission of the organic ELD.